Gas turbine engine component coating with self-healing barrier layer

ABSTRACT

A method of providing a self-healing coating includes providing substrate, applying a layer of an aluminum-containing MAX phase material and another material to the substrate. The method includes exposing the layer to a temperature greater than 2000° F. to form alpha aluminum.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.15/036,885, filed May 16, 2016 which is a U.S. National PhaseApplication of PCT/US2014/064023 filed Nov. 5, 2014, which claimspriority to U.S. Provisional Application No. 61/909,074, which was filedon Nov. 26, 2013 and is incorporated herein by reference.

BACKGROUND

This disclosure relates to a coating for components in applications suchas gas turbine engines and internal combustion engines.

Many gas turbine engine components are subject to temperatures in excessof the melting temperature of the component substrate, which may beconstructed from a nickel superalloy or non-oxide ceramic, for example.Cooling features and thermal barrier or environmental coatings are usedto protect the substrate from these extreme temperatures.

Thermal barrier coatings (TBC) or environmental barrier coating (EBC)made from yttria-stabilized zirconia (YSZ) and gadolinium zirconiumoxide are typically used to reduce the temperature of cooled turbine andcombustor components. Additionally, these materials may also be used asabradable seal materials on cooled turbine blade outer air seals (BOAS)as well as other components. In these applications, there are severaldegradation and failure modes. During engine operation, thermal barriercoatings may become spalled, delaminated, chipped or eroded, forexample, due to debris or environmental degradation.

Bond coats for thermal barrier coatings as well as environmental barriercoatings for high temperature composite materials rely on an oxygendiffusion barrier layer that is often alpha alumina. Alpha alumina is anexcellent barrier to oxygen diffusion and naturally forms at elevatedtemperature on aluminum rich alloys. This layer is often referred to asa thermally grown oxide (TGO). As this TGO layer grows with time andtemperature it typically buckles and spalls off at which time it mustregenerate, drawing further from the aluminum reserves of the hostmaterial by diffusion. As the aluminum gets depleted, non-ideal oxidesbegin to form which make the TGO less effective at preventing furtheroxidation. Making TGO adhesion more difficult is the coefficient ofthermal expansion (CTE) mismatch between the metallic aluminum donor andalumina layers during the thermal cycling present in most applications.

SUMMARY

In one exemplary embodiment, a method of providing a self-healingcoating includes providing substrate, applying a layer of analuminum-containing MAX phase material and another material to thesubstrate. The method includes exposing the layer to a temperaturegreater than 2000° F. to form alpha aluminum.

In a further embodiment of any of the above, the layer provides a MAXphase/metal matrix composite.

In a further embodiment of any of the above, the substrate is at leastone of a nickel based alloy, an iron-nickel based alloy, a cobalt basedalloy, a molybdenum based alloy, or a niobium based alloy.

In a further embodiment of any of the above, sing a thermal barriercoating is applied to the layer.

In a further embodiment of any of the above, the layer is a bond coat.The other material is at least one of a MCrAlY material (where M isnickel, iron and/or cobalt), an aluminide material, a platinum aluminidematerial, or a ceramic-based material.

In a further embodiment of any of the above, the aluminum-containing MAXphase material has an aluminum ratio of 0.6-1.4 times a stoichiometricaluminum value of the MAX phase material.

In a further embodiment of any of the above, the thermal barrier coatingincludes at least one of an yttria stabilized zirconia material and agadolinia stabilized zirconia material.

In a further embodiment of any of the above, the substrate is anon-oxide ceramic including at least one of a ceramic based substrate ora ceramic matrix composite substrate.

In a further embodiment of any of the above, the non-oxide ceramic isSiC or SiN.

In a further embodiment of any of the above, the layer is anenvironmental barrier coating, and the other material is at least one ofan alumina-containing ceramic, mullite, zircon, or rare earth silicates.

In a further embodiment of any of the above, the aluminum-containing MAXphase material has an aluminum ratio of 0.6-1.4 times a stoichiometricaluminum value of the MAX phase material.

In a further embodiment of any of the above, the metal matrix is formedfrom particles having a particle size of 0.02 and 0.5 microns.

In a further embodiment of any of the above, the particles of the metalmatrix composite are formed via ball milling.

In a further embodiment of any of the above, the applying step comprisesco-spraying individual constituent MAX phase and metal matrix compositeparticles.

In a further embodiment of any of the above, the MAX phase material hasa particle size of between 1 and 3 microns.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure can be further understood by reference to the followingdetailed description when considered in connection with the accompanyingdrawings wherein:

FIG. 1 is a highly schematic view of a component with a self-healingbond coat supporting a thermal barrier coating.

FIG. 2 is a highly schematic view of a component with a self-healingenvironmental barrier coating supported on a substrate.

The embodiments, examples and alternatives of the preceding paragraphs,the claims, or the following description and drawings, including any oftheir various aspects or respective individual features, may be takenindependently or in any combination. Features described in connectionwith one embodiment are applicable to all embodiments, unless suchfeatures are incompatible.

DETAILED DESCRIPTION

A component 10 is schematically shown in FIG. 1. The component 10, whichmay be a turbine blade airfoil, for example. The component 10 may beused in a variety of gas turbine engine components applications,including but not limited to vanes, blades, blade outer air seals, fuelnozzle guides, combustor liners, exhaust liners, and augmenter liners.The component 10 may be used in a variety of internal combustion enginecomponent applications, such as exhaust manifolds, intake manifolds,valves, headers, turbo chargers, external waste gates, exhaust downpipes, exhaust systems, converters and mufflers.

The component 10 includes a substrate 12 that is formed from a material,such as a nickel based alloy, an iron-nickel based alloy, a cobalt basedalloy, a molybdenum based alloy, or a niobium based alloy. A bond coat14 is applied to the substrate 12, and a thermal barrier coating 16 isapplied to the bond coat 14. The thermal barrier coating 16 has anexterior surface on a hot side of the component. In the exampleillustrated, the thermal barrier coating 16 is the outermost layer ofthe component 10 on a hot side of the component. Additional layers maybe provided on the thermal barrier coating 16 covering the exteriorsurface, if desired.

The bond coat may be applied using any suitable technique known in theart. The bond coat 14 may be applied by low pressure plasma spray(LPPS), atmospheric plasma spray (APS), high velocity oxygen fuel(HVOF), high velocity air fuel (HVAF), physical vapor deposition (PVD),chemical vapor deposition (CVD) or cathodic arc, for example. Once thesubstrate surface is coated, the thermal barrier coating may be applied,for example, by using an electron beam physical vapor deposition (EBPVD)process, a suspension plasma spray (SPS), sputtering, sol gel, slurry,low pressure plasma spray (LPPS) or air plasma spray (APS), for example.

The thermal barrier coating 14 may comprise one or more layers of aceramic material such as an yttria stabilized zirconia material, agadolinia stabilized zirconia material, cubic/fluorite/pyrochlore/deltaphase fully stabilized zirconates where stabilizers are any oxide or mixof oxides including Lanthanide series, Y, Sc, Mg, Ca, or furthermodified with Ta, Nb, Ti, Hf. The thermal barrier coating may also behafnia based. The yttria stabilized zirconia material may contain from3.0 to 40 wt. % yttria and the balance zirconia. The gadoliniastabilized zirconia material may contain from 5.0 to 99.9 wt. %gadolinia, and in one example, 30 to 70 wt. % gadolinia and the balancezirconia.

The bond coat 14 may be either a MCrAlY material (where M is nickel,iron and/or cobalt), an aluminide material, a platinum aluminidematerial, or a ceramic-based material. NiCoCrAlY bond coat and anyttria-stabilized zirconia (YSZ) thermal barrier coating may be used toprovide the disclosed bond coat 14 and thermal barrier coating 16, forexample. Of course, numerous other ceramic layers may be used. MCrAlYcoatings also include MCrAlYX coatings, where X is at least one of areactive element (Hf, Zr, Ce, La, Si) and/or refractory element (Ta, Re,W, Nb, Mo).

In addition to the above bond coat materials, the bond coat 14 includesa MAX phase material, which forms a MAX phase/metal matrix composite. AMAX phase material is a group of ternary carbides with the formulaM_(n+1)AX_(n) (where n=1-3, M is an early transition metal, A is anA-group element and X is carbon and/or nitrogen). Desired MAX phasematerials for the bond coat 14 include aluminum as the A-group element,which provides an aluminum rich source for thermally grown oxides havinga high aluminum diffusion rate. Example MAX phase materials includeCr₂AlC, Ti₂AlC, Ti₂AlN and Ti₃AlC₂. Niobium-, tantalum- andvanadium-based MAX phase materials may also be used.

Aluminum-containing MAX phase materials having an extremely highdiffusion rate of aluminum along the basal plane direction as well asprovide phase stability of materials to as little as 0.6 of thestoichiometric aluminum ratio. One example desired amount of aluminumratio in the MAX phase material is 0.6-1.4 the stoichiometric value,which provides high aluminum mobility. As a result, a bond coat 14 isprovided that forms a high purity alumina TGO with rapid self-healingproperties in temperatures above 2000° F. (1093° C.).

Example MAXMET (max phase/metal matrix composite) layer manufacturingmethods include co-spraying of individual constituent MAX phase andmetal matrix composite particles. The MAXMET particle size is, forexample, 0.02 to 200 microns (0.00079 to 7.90 mils). MAX phase particleshaving a size of 1-3 microns (0.039 to 0.12 mils) are available asMAXTHAL powder from Sandvik Materials Technology. One method ofproducing the metal matrix composite particles is ball milling theconstituents to mechanically alloy. This would produce a desirabledistribution and size of 0.02 to 0.5 microns (0.0079 to 0.020 mils). Thefiner MAX phase particles result in a more homogeneous composite andprovide optimal TGO growth uniformity.

The MAXMET material may be applied to the component by spraying theMAXMET particles by agglomeration, sintering, crushing of MAXMET, oratomization of a MAX particle suspension in a molten matrix (slush).Alternatively, a MAXMET preform may be manufactured and then bonded tothe part by diffusion bonding or brazing. MAXMET may also be applied bydirectly forming the layer on the surface by hot pressing constituentpowders or MAXMET particles.

Another component 18 is shown in FIG. 2. The substrate 20 is a non-oxideceramic, such as a SiC or SiN ceramic based substrate or a ceramicmatrix composite substrate. An environmental barrier coating 22 isapplied to the substrate 20. The environmental barrier coating 22 mayinclude an alumina containing ceramic, e.g., mullite, zircon (ZrSiO₄),rare earth silicates, combinations of at least one of the foregoing, andthe like. Suitable rare earth silicates include, but are not limited to,yttrium silicate, yttrium disilicate, magnesium aluminate spinel, andthe like.

The environment barrier coating 22 includes a MAX phase material asdescribed above with respect to the bond coat 14.

The disclosed coating provides a higher purity and more stable aluminaTGO layer than prior art oxidation resistant materials due to itsimproved ability to diffuse aluminum to the surface compared to priorart bond coat and aluminide materials. The MAX phase/metal matrixcomposite is highly damage tolerant, has reduced CTE mismatch with theTGO, larger aluminum reservoir and higher aluminum diffusion ratescompared the prior art coatings.

It should also be understood that although a particular componentarrangement is disclosed in the illustrated embodiment, otherarrangements will benefit herefrom. Although particular step sequencesare shown, described, and claimed, it should be understood that stepsmay be performed in any order, separated or combined unless otherwiseindicated and will still benefit from the present invention.

Although the different examples have specific components shown in theillustrations, embodiments of this invention are not limited to thoseparticular combinations. It is possible to use some of the components orfeatures from one of the examples in combination with features orcomponents from another one of the examples.

Although an example embodiment has been disclosed, a worker of ordinaryskill in this art would recognize that certain modifications would comewithin the scope of the claims. For that reason, the following claimsshould be studied to determine their true scope and content.

What is claimed is:
 1. A method of providing a self-healing coating,comprising: providing a substrate; applying a layer to the substrate,the layer comprising aluminum-containing MAX phase material and anothermaterial, wherein the layer provides a MAX phase/metal matrix composite,and wherein the MAX phase material has a particle size pf between 1 and3 microns; and exposing the layer to a temperature greater than 2000° F.to form alpha aluminum.
 2. The method according to, wherein thesubstrate is at least one of a nickel based alloy, an iron-nickel basedalloy, a cobalt based alloy, a molybdenum based alloy, or a niobiumbased alloy.
 3. The method according to claim 1, comprising applying athermal barrier coating to the layer.
 4. The method according to claim3, wherein the layer is a bond coat, and the other material is at leastone of a MCrAlY material (where M is nickel, iron and/or cobalt), analuminide material, a platinum aluminide material, or a ceramic-basedmaterial.
 5. The method according to claim 3, wherein thealuminum-containing MAX phase material has an aluminum ratio of 0.6-1.4times a stoichiometric aluminum value of the MAX phase material.
 6. Themethod according to claim 3, wherein the thermal barrier coatingincludes at least one of an yttria stabilized zirconia material and agadolinia stabilized zirconia material.
 7. The method according to claim1, wherein the substrate is a non-oxide ceramic including at least oneof a ceramic based substrate or a ceramic matrix composite substrate. 8.The method according to claim 7, wherein the non-oxide ceramic is SiC orSiN.
 9. The method according to claim 7, wherein the layer is anenvironmental barrier coating, and the other material is at least one ofan alumina-containing ceramic, mullite, zircon, or rare earth silicates.10. The method according to claim 9, wherein the aluminum-containing MAXphase material has an aluminum ratio of 0.6-1.4 times a stoichiometricaluminum value of the MAX phase material.
 11. The method according toclaim 1, wherein the metal matrix is formed from particles having aparticle size of 0.02 and 0.5 microns.
 12. The method according to claim11, wherein the particles of the metal matrix composite are formed viaball milling.
 13. The method according to claim 1, wherein the applyingstep comprises co-spraying individual constituent MAX phase and metalmatrix composite particles.